I am not using Cs, but for you, I found some documents on the isotope 137 of caesium:
Kershaw, P.J. et Baxter, A.J. (1995). The transfer of reprocessing wastes from NW Europe to the Arctic. Deep-Sea Research, II 42 (6): 1413-1448.
Kershaw, P.J., McCubbin, D. et Leonard, K.S. (1999). Continuing contamination of north Atlantic and Arctic waters by Sellafield radionuclides. Sci Total Environ, 237-238: 119-132.
Koulikov AO et Meili M (2003). Modelling the dynamics of fish contamination by Chernobyl radiocaesium: an analytical solution based on potassium mass balance. J Environ Radioactiv,66: 309-326.
Madoz-Escande C, Bréchignac F et Colle C (1999). Experimental installations for radioecology research on defined ecosystems subjected to contamination in controlled conditions. Nuc Sci Eng,133: 178-191.